THE CCELOMTC FLUID IN ACANTHODRIIJDS. 581 



cytes. The great consistenc}', aud the absence of ready flow^ 

 which is so noticeable a feature, as compared with the fluid of 

 Lnmbricids, is related no doubt to the abundance of cell 

 elements and small proportion of lic{nid plasma. But this 

 plasma itself must be mncli less fluid than blood-plasma, for, 

 as above mentioned, a drop of the fluid is sufficiently firm to 

 support a cover-slip, and yet the cells are protected from 

 bursting or injury; indeed, the}' are but slightly compressed 

 except at the margins of the drop. 



The fluid appears to " coagulate " rapidly, but 1 have been 

 unable to detect any fibrin-like threads except after exposure 

 to air for some time. 



The stuff is sticky; adheres to the glass, or dish, or fingers. 



The dish in which the worm was kept during examination 

 of the fluid soon became coated at the bottom with a 

 tenacious slime, becoming slightly buff coloured after a time. 

 This slime when lifted seems stringy, and fine threads, fibrin- 

 like, hold the corpuscles together. Rut these have no rela- 

 tion, so far as I could discover, to the threads in the linocytes. 

 I imagine they are chemically produced in the plasma. 



Octochfetus multiporus and 0. antarcticus are 

 highly photogenic or phosphorescent, and when handled in 

 the dark it is at once seen that this light has its seat in the 

 ccelomic fluid as it issues from the dorsal pores and slowly 

 spreads over the surface of the worm. The effect is much 

 more brilliant if the worm be stimulated by a little vapour of 

 acetic acid; then the abundantly discharged fluid gleams 

 with considerable brilliance. 



It has been suggested (Beddard, 'Nature,' vol. Ix, p. 52) 

 that the photogeny of Microscolex modestus aud of 

 Allolobophora fcetida is due to photogenic bacteria; but 

 as I have indicated (loc. cit., p. 591) there is reason to be- 

 lieve that the phenomenon is connected with the eleocytes 

 of the fluid. It is well known that in a number of animals 

 photogeny occurs in direct association with cells containing 

 fatty matters; and that it is by no means always or neces- 

 sarily associated with the presence of bacteria (for example, 



